U.S. Pat. No. 3,787,230 discloses a method for coating an article by applying an aqueous slurry of a powder paint onto the surface. The powder paint is a commercial powder, having an average particle size of 36 micrometers, and the slurry has to be kept homogeneous by agitation during preparation and use. On storage the solid matter of such a slurry will settle, and it is technically unattractive to redisperse it again immediately before use.
Further, U.S. Pat. No. 4,100,315 discloses a method to prepare aqueous coating powder dispersions containing as the binder a solid epoxy resin, which is micronized in water in the presence of a specific combination of surfactants. For many applications, however, the presence of surfactants in the cured coating is not desirable.
Epoxy resin/amine adducts have been used before in aqueous coating compositions, which were mainly intended for cathodic electrodeposition, and in which the amino component was at least partly neutralized with an acid before being diluted with water. The neutralization served to make the amine water-soluble, and also to provide the necessary positive electrical charge on amino groups for cathodic electrodeposition; usually from 20 to 100% of the amine adduct was neutralized. See, for example, British Pat. Nos. 1,235,975 and 1,461,832, U.S. Pat. Nos. 3,962,499 and 4,150,006.